It is well known that cylinders are widely used in various plants. An oil-pressure cylinder is normally used when high thrust is needed to push a row of platform trucks, especially ones whose total weight exceeds one hundred tons. Electric cylinders are mainly used when no particularly high thrust is needed.
If the above-mentioned oil-pressure cylinder can be replaced by an electric cylinder, the cylinders used in a plant can be combined into one type of electric cylinder. Such unification is very advantageous for their maintenance.
However, the manufacture of a high-thrust electric cylinder with thrust high enough to replace the oil-pressure cylinder is very difficult, because ball screws for both high-load and small-lead use are seldom on the market and are rarely available. Moreover, due to extraordinarily high cost it is not practical to either manufacture ball screws by oneself or have them custom-made. Thus, the necessity of using both oil-pressure and elecric cylinders is unavoidable and causes great inconvenience in maintaining the cylinders.